RESUMO
Nitric Oxide(NO) has been known to be endothelium-derived relaxing factor in blood vessels, and to be nonadrenergic-noncholinergic(NANC) neurotransmitter involved in the relaxation of corpus cavernosum smooth muscle of man and rabbit. This study was initiated to determine NANC inhibitory neurotransmission in the canine corpus cavernosum. Using organ bath, isometric tension measurements were made in strips of canine corpus cavernosum. Transmural electrical stimulation of corporal tissue strips, in the presence of adrenergic blockade with bretylium and muscarinic receptor blockade with atropine, caused frequency-dependent relaxation. This relaxation was inhibited significantly by nitric oxide synthase inhibitor, N-nitro-L-arginine methyl ester(L-NAME). Our findings suggest that there should be nonadrenergic-noncholinergic neurotransmitter in the canine corpus cavernosum smooth muscle and it could be nitric oxide. Canine erectile tissue might serve as in vitro model for further investigation of corpus cavernosal smooth muscle pathophysiology.